Chapter06

Chapter 6: Dates and Times

6.1 Finding Today’s Date

Problem

You want to find today’s date and/or time.

Solution

Invoke the appropriate builder to obtain a LocalDate, LocalTime, or LocalDateTime object and call its toString() method.

In full-scale applications, it’s recommended to pass a Clock instance into all the now() methods.

6.2 Formatting Dates and Times

Problem

You want to provide better formatting for date and time objects.

Solution

Use java.time.format.DateTimeFormatter.

6.3 Converting Among Dates/Times, YMDHMS, and Epoch Seconds

Problem

You need to convert among dates/times, YMDHMS, epoch seconds, or some other numeric value.

Solution

Use the appropriate date/time factory or retrieval methods.

6.4 Parsing Strings into Dates

Problem

You need to convert user input into java.time objects.

Solution

Use a parse() method.

6.5 Difference Between Two Dates

Problem

You need to compute the difference between two dates.

Solution

Use the static method Period.between() to find the difference between two LocalDates.

6.6 Adding to or Subtracting from a Date

Problem

You need to add or subtract a fixed period to or from a date.

Solution

Create a past or future date by using a locution such as Local⁠Date.plus(Period.ofDays(N));.

6.7 Handling Recurring Events

Problem

You need to deal with recurring dates, for example, the third Wednesday of every month.

Solution

Use the TemporalAdjusters class.

6.9 Interfacing with Legacy Date and Calendar Classes

Problem

You need to deal with the old Date and Calendar classes.

Solution

Assuming you have code using the original java.util.Date and java.util.Calendar, you can convert values as needed using conversion methods.